Turbine blades, especially turbine blades for gas turbines, during operation are exposed to high temperatures which possibly also exceed the limit of the material stress. This especially applies to the regions in the vicinity of the flow inlet edge of the turbine blades. In order to be able to use turbine blades even at high temperatures it has already been known for a long time to suitably cool turbine blades so that they have a higher resistance to temperature, wherein the importance of blade cooling constantly increases especially in the case of gas turbines on account of the increasing gas-turbine inlet temperatures. With turbine blades which have a higher resistance to temperature, higher energy efficiencies in particular can be achieved.
Known types of cooling are inter alia convection cooling, impingement cooling and film cooling. In the case of convection cooling, it is probably the most widespread type of blade cooling. With this type of cooling, cooling air is guided through passages inside the blade and the convective effect used to dissipate the heat. In the case of impingement cooling, a cooling air flow from inside impinges upon the surface of the blade. In this way, a very good cooling effect is made possible at the point of impingement, which is limited, however, only to the narrow region of the impingement point and the immediate vicinity. This type of cooling is therefore mostly used for cooling the flow inlet edge of a turbine blade, which is exposed to locally high temperature stresses. In the case of film cooling, cooling air is guided from inside the turbine blade outwards via holes in the turbine blade. This cooling air flows around the turbine blade and forms an insulating layer between the hot process gas and the surface of the blade. The described types of cooling, depending upon the application case, are suitably combined in order to achieve blade cooling which is as effective as possible.
An impingement-cooled inlet edge of a turbine blade is known for example from U.S. Pat. No. 6,238,182. The turbine blade comprises a cast blade airfoil profile with a comparatively thick profile wall in which a thin-walled impingement-cooling insert is fitted. The impingement-cooling insert is supported via a plurality of ribs, which in case taper to a point, on ribs which lie opposite these and which in their turn are provided on the inner sides of the profile wall. The rib-pairs which are formed in this way are soldered together in this case so that these enclose chambers.
For realizing a convection cooling, in the case of currently known designs of turbine blades, the blade including a shell, for example in the form of a blade jacket, and cooling passages, is cast. Additional coatings are applied by means of coating processes. In this case, the producing of the cooling passages which are formed in known turbine blades, which is undertaken by means of a casting process, is particularly very time-consuming and cost-intensive.
In addition to a turbine blade which is produced in the casting process, it is also known from U.S. Pat. No. 2,906,495 to assemble purely convectively coolable turbine blades from a support structure and a shell. The support structure in this case is formed in a corrugated-like manner. The corrugation valleys and the corrugation peaks are either soldered to the suction side or to the pressure side of a blade airfoil profile which is formed by a shell, as a result of which a plurality of cooling passages extend linearly along the blade airfoil profile.